This application is a xc2xa7371 national stage of PCT International Application No. PCT/IN00/00120, filed Jun. 12, 2000, designating the United States of America, which claims priority of Indian Application No. 892/BOM/99, filed Jun. 12, 1999, the contents of which are hereby incorporated by reference.
1. Technical Field
The present invention relates to a fuel-efficient steam cooking device that saves more than 70% of the fuel consumed by conventional steam cooking systems. In addition, the device is safe and easy to operate and manufacture. The cooking device of the invention operates primarily on steam and requires slow cooking, whereby good flavor is imparted to the food cooked in the system.
2. Background Art
The traditional method of cooking is by boiling the food or simmering in a vessel with an open top. In some cases, the top is covered by a lid. Food is placed inside the vessel with adequate quantity of water and the bottom of the vessel is placed directly on the flame. This is shown in FIG. 1.
Cooking in the device of FIG. 1 takes place as the temperature in the cooking vessel rises to 100xc2x0 C., and is maintained at that temperature until cooking is complete. The food may or may not be stirred while the cooking is in progress. If the flame is quite strong and there is insufficient water in the vessel, there is a possibility of the food which is in contact with the bottom of being charred.
U.S. Pat. No. 2,097,478 discloses a cooking utensil comprising an outer vessel that supports an inner vessel in lowered and raised positions. The outer vessel includes a cylindrical flange that is permanently fitted within a circumferential trough in the wall of the outer vessel. The outer vessel is adapted to support the inner vessel thereby requiring the vessels to be purchased as a combination. Also, the support flanges in the cooking utensil may prove a hindrance when trying to clean the utensil.
Similarly, the prior art has yet another cooking utensil called Rukmini cooker as shown in FIG. 2, comprising a stack of cylindrical cooking vessels that fit one on top of the other, with a lid over the upper-most cooking vessel. Each cooking vessel may contain a different food item. The entire assembly is held together by a lifting frame or cradle, so that it can be lifted as a single unit. This assembly is then lowered into a deep container of slightly larger diameter, which has water at the bottom. This deep outer container has a tight-fitting lid. It is placed on a stove usually of the same diameter as the outer container. The water in the deep outer container gets converted into steam when heated and this steam helps in cooking the food within the cooking vessels. This steam condenses, returns to the base as water, and is once again converted to steam. The temperature of the food in the cooking vessels is gradually raised to 100xc2x0 C., and maintained at that temperature as long as steaming continues. The advantage of this cooker is that several food items are cooked simultaneously, and that the food requires no stirring since it cannot be charred by overheating. The disadvantage is that the heat energy dissipates from inside to outside and hence, significant fuel is burnt to cook the food using this cooker. In addition, as the outer container is hot, it is not safe.
A somewhat similar steam cooker, without the outer vessel of the Rukmini cooker, is shown in FIG. 3. This cooker consists of a stack of cylindrical cooking vessels placed directly on the flame. The lowest vessel contains water only. The steam produced is passed into the upper vessels in various ways. Some vessels have a perforated bottom. Other vessels are fitted with a central pipe which serves to carry steam, into the vessels above the basal vessel.
Another instance of a cooking vessel in the prior art is the Haybox or Insulation Cooker, which is shown in FIG. 4. It consists of a thermally insulating chamber with a thermally insulating lid. Food is brought to boiling point in a vessel, but is not yet fully cooked. It is covered with a lid, and is then placed in the Haybox. The insulating lid of the Haybox is put into place, and the whole assembly is left undisturbed for a while. The food inside the cooking vessel continues to cook in its own heat. Fuel economy results because part of the cooking takes place in the insulating chamber, with no explicit supply of heat.
Industrial kitchens and canteens, where cooking is carried out in bulk, often use steam cookers, shown in FIG. 5. Such cookers consist of double-walled double-bottomed stainless steel vessels, where food is placed in the inner vessel. Steam is generated from a separate source such as a separate boiler, and is circulated in the gap between the double walls and double bottoms of the cooking vessels. Condensed steam collects in the outer bottom, from where it is piped back to the boiler. The food in the inner vessels has its temperature raised to 100xc2x0 C., and it is maintained there until cooking is complete.
Pressure Cookers, as shown in FIG. 6, work on the principle of raising the boiling point to a higher temperature, usually about 120xc2x0 C. at about 2-atmosphere pressure. The food is placed in one or more containers, which are then placed inside an outer container with water at the base. The outer container is then closed with an air-tight lid equipped with a safety valve, which does not allow the pressure within to build up over about 2 atmospheres. As the outer container is heated, the temperature within rises to 120xc2x0 C. A further rise in temperature is prevented by the safety valve allowing steam to escape so that the pressure within is restricted to about 2 atmospheres. Because of the elevated temperatures, the food cooks more quickly, and there is some saving in fuel consumption. There is little or no danger of charring of the food so long as the water remains in the outer container. Pressure cookers are popular because they reduce the time taken to cook food. The disadvantage is that manufacturing the pressurized container, its lid and seal is a complex process; and that there is always a danger of explosion should the safety valve get stuck. Further, the steam escapes from the cooker expelling the flavour and fragrance of the food cooking in the cooker and hence, some aroma and taste of the food is also lost. Furthermore, there is always a possibility of the food being overcooked.
U.S. Pat. No. 6,078,029 provides an efficient cooking range system, which maximizes the contact between the heating element of a cooking range and the cooking pot. The cooking device of this patent is shown in FIG. 7. An insulating air is provided on the interior base and the interior perimeter side wall of the cooking well which is present in the cooking pot. This system has several disadvantages including the fact that all the elements need to be purchased as a combination. This cooking system occupies a lot of space and is un-economic. In most of these systems, fuel economy is not a significant consideration. Moreover, steam is not used as a medium to transmit heat energy in other parts of the vessel.
While the cooking devices of prior art fulfil the respective objects and requirements, the prior art lacks a cooking device which is simple, easy to manufacture, allows slow and proper cooking and economizes on the fuel consumed. Accordingly, there is a need for a cooking device which economizes on fuel, is safe and easy to handle and imparts flavour and taste to food.
The main object of the invention is to provide an efficient cooking device that saves more than 70% of the fuel consumed by conventional cooking systems.
Another object is to provide a cooking device wherein cooking is effected by circulation of steam.
Yet another object of the invention is to provide a cooking device which is safe and has none of the hazards of explosion associated with pressure cookers.
Another object is to provide a cooking device wherein the cooking of the food items is effected slowly so that the flavour and taste of the food is retained.
Still another object of the invention is to provide a cooking device wherein several food items can be cooked simultaneously, instead of sequentially.
Another object is to provide a cooking device in which there is no danger of the food burning, or of the food attaining elevated temperatures which would affect the flavour and quality of the cooked food.
Still another object is to provide a cooking device wherein any conventional source of fuel, such as gas, kerosene, coal, wood or cow-dung and electricity can be used for cooking food.
One more object is to provide an efficient cooking device that uses simple technology and can be manufactured at low cost in regard to materials and labour and can be sold at affordable rates.
The invention provides a novel cooking device that saves more than 70% fuel as compared to conventional cooking systems and comprises:
(i) a basal receptacle,
(ii) a series of cooking utensils, and
(iii) inner cover and outer cover, both engaged firmly to the basal receptacle.
As mentioned in the foregoing section, several cooking utensils are known in the prior art. One typical utensil is depicted in FIG. 1, wherein the utensil consists of a simple vessel (1) provided with a lid (2). A modification of this cooking utensil i.e. Rukmini cooker is shown in FIG. 2 which cooker has an outer vessel (3) into which are placed a series of cooking vessels (4). This cooker is provided with a lid (5). It may optionally be provided with a stand (6) and the cooking vessels may be provided with a cradle or lifting frame (7). Another steam cooker is shown in FIG. 3 wherein a stack of cooking vessels (8) is provided with lid (9) and pipes (10) to carry steam to each cooking vessel. Some of the vessels of this cooker have a perforated bottom.
The Haybox cooker shown in FIG. 4 is yet another cooking system, having a thermally insulating chamber (11) with a thermally insulating lid (12). A vessel (10A) is kept in this chamber. For cooking, the food in the vessel is brought to boiling point and when the food is still uncooked, the vessel is placed in the Haybox. The Haybox is covered with a lid and the entire assembly is left undisturbed for completion of cooking. In Industrial Canteens where cooking is carried out in bulk, a steam cooker, as shown in FIG. 5, is used. This cooker consists of a double bottomed stainless steel vessels (14) and lid (15). The steam is generated from a separate source such as boilers and this steam is supplied to the gap between the walls and bottom of the cooking vessels through an inlet (13A). Steam circulates in the gap. The condensed steam is collected through a bottom outlet (13) and is piped back to the boilers. The temperature of the food is elevated and maintained as such until cooking is complete. Another cooking device working on steam is the pressure cooker as shown in FIG. 6, wherein food placed in one or more containers (16) and placed in an outer container (17) and closed with lid (18) having safety valve (18A). If the outer container is heated, the temperature within the system rises and pressure builds up on account of which, food in the system is cooked. Yet another cooking system can be seen in FIG. 7, which system consists of cooking utensils provided with an insulator on the interior base and the interior perimeter side walls of the cooking utensils. As each of the above cooking systems are constructed with certain specific objectives, there is no system in the prior art which is constructed with the focus of saving fuel and cooking food with the help of steam. In addition, none of the prior art cookers employ a thin layer of stagnant air located between the inner and outer covers to provide proper heat insulation.
Accordingly, the invention provides a novel and fuel-efficient cooking device as shown in FIGS. 8 to 15 of the accompanying drawings. The focus of the invention is to provide a cooking device wherein the process of cooking is effected slowly and the fuel consumed for cooking is saved to the extent of more than 70%.